Air volume control sound trap



y 1967 G. K. RAIDER ETAL 3,319,559

AIR VOLUME CONTROL SOUND TRAP Filed July 1-5, 1965 2 Sheets-Sheet 1 INVENTORS G-ozes Z fl/pae m ATTORNEYS y 16, 1967 G. K. RAIDER ETAL. 3,319,559

AIR VOLUME CONTROL SOUND TRAP 2 Sheets-Sheet 2 Filed July 13, 1965 INVENTORS GOFG K @052 foMu/vo J (/7716 m, ATTORNEYS United States Patent Ofifice 3,319,559 Patented May 16, 1967 3,319,559 AIR VGLUME CONTRGL SOUND TRAP George K. Raider, Melrose Park, and Edmund J. Little, Ch cago, Ill., assignors to The Pyle-National Company, Chicago, 111., a corporation of New Jersey Filed July 13, 1965, Ser. No. 471,691 3 Claims. (CI. 98-40) This invention relates to an air volume control sound trap for returning air from a plurality of rooms to a common plenum and wherein the movable air control member of the device has sound absorbent material thereon to control the attenuation of sound from one room or space to another.

Current developments in heating, lighting and ventilation equipment have led to the widespread use of double ceiling construction in office buildings, places of manufacture and the like. Essentially, double ceiling construction involves a principal structural ceiling and a false or inner ceiling spaced apart to provide a plenum for receiving the air and power distribution systems.

It has been found, however, that while such construction leaves distribution equipment highly accessible and therefore easily adaptable to changing requirements, such construction also enables the ready transmission of sound energy throughout the plenum. As a result, local noises and other sounds may be carried to distant locations, which is highly undesirable in many environments such as ofiice, hospital, or other ward type establishments.

To rectify this circumstance, walls may be erected to the structural ceiling which may otherwise have terminated at the inner ceiling. This solution to noise transmission is not only costly but highly obstructive to the general functional purpose of a common plenumname- 1y, accessibility and flexibility of the air distribution system.

Moreover, in systems using air trolfer ceiling installations, so-called slot diffusers used in association or combination with the trofier lights are used to return air to a common plenum above the ceiling for the purpose of heat pick-up. That heat can then be utilized elsewhere, for example, in heating areas at the outer periphery of the building. Sound can be transfer-red. from room to room covered by a common plenum. Accordingly, this invention solves that problem by providing a sound trap with a control to govern the air being returned from each individual space.

Therefore, it is an object of this invention to provide an air distribution system utilizing a common plenum and which generally attenuates noises developed within that system.

It is also an object of this invention to provide a sound trap device for direct connection to an air distribution unit.

It is another object of this invention to provide a sound trap device in the form of an air volume control.

It is a further object of this invention to provide a sound trap volume control device for being cooperably mounted at diifuser slots formed within a troifer light fixture.

These and other objects, features and advantages of the present invention will be understood in greater detail from the following description in which an exemplary apparatus embodying the principles of the present invention is shown by way of illustration.

On the drawings:

FIGURE 1 illustrates a multi-unit structure having a common plenum and employing troifer light fixtures meeting the specifications of this invention;

FIGURE 2 shows a trofier light fixture isolated from its Working environment and illustrating the sound attenuation device of this invention;

View of the troifer light fixture as illustrating the comparative and of the sound attenuation struc- FIGURE 3 is a top shown in FIGURE 2 symmetrical positioning tures;

FIGURE 4 is an enlarged sectional view of the trofier light fixture having the sound attenuation attachments of this invention and illustrating the adjustable volume control features; and

FIGURE 5 is a side view of the troifer light fixture of FIGURE 4 showing the relative positioning of the volume control adjustment device.

As shown on the drawings:

This invention is directed to the attenuation of sounds which are readily transmitted through ventilating devices which are common to several rooms or'areas. A common or central ventilating system is a highly desirable, efiicient and necessary improvement for many structures, but the desirability of such a system can be greatly nc-' gated by the undesirable transmission of unwanted noises and other sounds.

- This invention has greatly reduced the sound transmis- V sion problem by providing a means for trapping sound energy while permitting the uninterrupted flow of air through the distribution system. In particular, this invention utilizes a perforated air transmission passageway having a relatively high ratio of closed to open areas. In addition, a sound absorbing medium is employed within the specialized perforated passageway which is both a sound absorption device and a volume control. The effeet is that sound is initially impeded within the highly enclosed passageway and channeled to the vicinity of the sound absorbing medium. The result is that while pressurized air is directed through the air passages formed in the walls, sound energy is trapped and absorbed within the sound absorbing medium.

A somewhat diagrammatic working environment for the structure of the invention is shown in FIGURE 1' in the form of a building structure having multiple spaces to be ventilated and illuminated such as rooms, ofiices or Wards 10 and 11 separated by a partition 12. For. convenience, this example is directed to adjacent rooms, but the principles of the present invention can be used in any organization wherein the problem of sound transmission occurs within a ventilating system. The entire structure shown in FIGURE 1 is intended to be disposed directly beneath a structural ceiling 13 which has been broken away to illustrate additional details of construction including a common plenum 14 formed above the inner ceiling 15. Also, each room is shown as provided with a single trofter light fixture shown generally at 16, however, it is to be understood that a typical air trolfer system would use many fixtures, some functioning only as troffer lights, some functioning as air supply fixtures, and some functioning as air returns, as do the fixtures 16 of FIGURE 1.

Heretofore, such light fixtures have been provided with difiuser slots for allowing the return of air either from the spaces being ventilated to a common plenum or from an air supply concealed behind the false ceiling to the various connected rooms.

When used as an air return, the fixtures 16 are used to return air from the spaces 10 and 11 to the plenum 14. That heat can then be utilized in some other location. For example, a blower 17 is shown as having an inlet 18 connected by a suitable duct 19 to an opening 20 formed in the wall of the plenum 14.

The blower 17 discharges the heated return air through an outlet 21 to a point of utilization depicted by the arrow 22, for example, the periphery of the architectural structure in which the spaces 10 and 11 are located.

To avoid transmission of sounds between rooms 10 and d 11 connected by the common plenum 14, it is contemplated by this invention to provide a sound trap device indicated generally by the numeral 23 for the fixture 16 and the details thereof may be more clearly seen in the enlarged views of FIGURES 2-5, inclusive.

The troffer light fixture is shown to comprise a truncated casing 24 for housing fluorescent-type lights represented by the bulbs 25. The casing 24 is provided with outwardly extending supporting flanges 26, each having an elongated slot 27 formed longitudinally therein. The sound trap device 23 comprises a rectangular chamber having spaced parallel elongated side walls 28 and capped ends 29. The walls 28 may have air diffusion passages formed therein as at 30, for example, by forming the Walls as foraminous members which prescribe a predetermined open area.

The sound trap device 23 with its open bottom wall in communicating registry with the slot 27 has a right angle bracket 31 provided between the upper panel 32 of the casing 24 and the upper surface 33 of the sound trap element 23 secured by fasteners such as a pair of sheet metal screws 34.

The sound trap device 23 has perforated side walls 23 formed with upturned edges 35 which are force-fitted between the rib guide 36 and a plurality of locator buttons 37 protruding from the face of the vertical base wall 38 of the truncated casing 24. The upper support for the sound trap element is provided by the bracket 31 as secured by the sheet metal fasteners 34.

The internal structure of each sound trap device 23 can best be understood by reference to FIGURE 4 wherein is shown an air volume control means 39 comprising an adjustable piston disposed within the sound trap device 23. The sound trap device 23 operates as a cylinder in which the piston moves and the piston has side walls 40 and 41 contiguous with the adjoining walls 28, 28 of the sound trap device 23. The walls 40 and 41 of the piston are connected by a transverse wall 42.

The piston 39 is threadedly received about an adjustment stem 43 disposed parallel to the perforated side walls 28 and an adjustment head 44 formed with a tool-receiving slot 45 is positioned within the vicinity of the diffuser slot 27 for access by an operator whenever air volume control at the specific outlet is desired to be adjusted.

The stem 43 is suspended from the upper sound trap surface 33 by a pin 46 and is provided with a lower bearing surface 47 fitted about the neck of the adjustment head 44, thereby making the stern translation limited and effecting adjustment of the piston 39 whenever the stem is rotatably adjusted.

Rotation of the threaded stem 43 will alter the relative position of the piston 39 within the sound trap element, thereby successively adjusting the number of air passages which are available for carrying air through the device, in order to adjust the rate of flow through the perforated side walls 28.

In accordance with this invention, a sound absorbing medium 48 is secured between the legs 40 and 41 of the piston 39 in confronting registry with the diffuser slot 27, thereby to absorb sound energy channeled between the substantially closed side walls 28.

Generally, the adjustment stem 43 is spaced substantially centrally of the sound trap device 23 for carrying the adjustable piston 39 within the interior of the sound trap device 23. The stem 43 is supported at three points. First, the stem 43 is threaded within a support collar 49 which is rigidly mounted to the transverse wall 42 of the adjustable piston 39.

Secondly, the stem 43 is suspended by the pin 46 at a bearing plate 50 disposed at the upper surface 33 of the sound trap element 23.

Thirdly, the stem 43 is maintained against a lower bearing surface 47 which is firmly mounted at the side walls 28. Therefore, rotation of the adjustment head 44 will result in a progression of the piston 39 in an upward or downward direction as determined by the rotation sense.

By adjusting the air flow in this manner, the sound absorbing medium 48 is always in direct registry with the diffuser slot 27, thereby constantly providing an improved attenuation of sound transmission in the direct path of the sound waves. Accordingly, the sound waves must either engage the sound absorbing medium or the direction of the sound waves will be changed in passing through the air passages in the side walls 28.

Although minor structural modifications might be suggested by those versed in the art, it should be understood that we wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of our contribution to the art.

We claim as our invention: 1

1. An air volume control sound trap comprising a sound trap enclosure for being disposed about an air flow said sound trap enclosure having a port for conducting from said air flow passage and having perforated side walls for distributing an air flow therethrough,

said perforated side walls having a surface area substantially greater than the area enclosed by said port of said sound trap enclosure,

a volume control piston slidably fitted within said sound trap enclosure and contacting said perforated side walls at the periphery thereof for defining a sound trap volume intermediate said volume control piston and said port of said sound trap enclosure,

said volume control piston having a sound absorbing medium disposed thereon and facing said port of said sound trap enclosure, and

control piston within said sound trap enclosure,

thereby controlling the volume of air flow through said port.

2. In a troffer light fixture having an external flange formed at opposite sides thereof and an elongated diffuser slot formed within each of said external flanges, an air volume control sound trap comprising a rectangular shaped enclosure having a port conforming substantially to said diffuser slot and mounted thereabout at said external flange, i

said rectangular shaped enclosure having side walls extending to a substantial height above said port in comparision to the width of said diffuser slot, said side walls having plural air passages formed therein,

a volume control piston slidably fitted within said sound trap enclosure and contacting said side walls at the periphery thereof,

said volume control piston having a sound absorbing medium disposed thereon and facing said port of said sound trap enclosure, and

means for adjusting the axial position of said volume control piston within said sound trap enclosure, thereby providing a means for regulating the flow of air while absorbing sound.

3. The combination of a troffer light fixture having an external flange formed at opposite sides thereof and an elongated diffuser slot formed within each of said external flanges and an air volume sound trap at said diffuser slot,

said diffuser slot having a generally elongated rectangular shape wherein the width thereof is a small fraction of the length thereof,

said air volume sound trap having spaced parallel elongated side walls, capped ends and a top wall together forming a rectangular chamber having a rectangular port conforming to said diffuser slot to allow air to pass into said sound trap through said slot and port,

said side walls having a height which is a large multiple of the width of the slot and which is a small fraction of the length of said slot.

means for adjusting the axial position of said volumew said side walls having plural air passages formed therein,

a volume control piston slidably fitted within said sound trap enclosure and having a rectangular cup-shaped configuration conforming substantially to said slot and including side walls connected by a transverse wall, said piston engaging said side walls and said ends at the periphery of said chamber to successively cover and uncover said passages relative to said port upon movement of said piston, said volume control piston having a sound absorbing medium secured to and filling the space between said side walls and facing said port of said sound trap enclosure, and

means for adjusting the vertical position of said volume control piston within said sound trap enclosure,

thereby providing a means for regulating the flow of air through said port while absorbing sound.

References Cited by the Examiner UNITED STATES PATENTS ROBERT A. OLEARY, Primary Examiner. W. E. WAYNER, Assistant Examiner. 

2. IN A TROFFER LIGHT FIXTURE HAVING AN EXTERNAL FLANGE FORMED AT OPPOSITE SIDES THEREOF AND AN ELONGATED DIFFUSER SLOT FORMED WITHIN EACH OF SAID EXTERNAL FLANGES, AN AIR VOLUME CONTROL SOUND TRAP COMPRISING A RECTANGULAR SHAPED ENCLOSURE HAVING A PORT CONFORMING SUBSTANTIALLY TO SAID DIFFUSER SLOT AND MOUNTED THEREABOUT AT SAID EXTERNAL FLANGE, SAID RECTANGULAR SHAPED ENCLOSURE HAVING SIDE WALLS EXTENDING TO A SUBSTANTIAL HEIGHT ABOVE SAID PORT IN COMPARISON TO THE WIDTH OF SAID DIFFUSER SLOT, SAID SIDE WALLS HAVING PLURAL AIR PASSAGES FORMED THEREIN, A VOLUME CONTROL PISTON SLIDABLY FITTED WITHIN SAID SOUND TRAP ENCLOSURE AND CONTACTING SAID SIDE WALLS AT THE PERIPHERY THEREOF, SAID VOLUME CONTROL PISTON HAVING A SOUND ABSORBING MEDIUM DISPOSED THEREON AND FACING SAID PORT OF SAID SOUND TRAP ENCLOSURE, AND MEANS FOR ADJUSTING THE AXIAL POSITION OF SAID VOLUME CONTROL PISTON WITHIN SAID SOUND TRAP ENCLOSURE, THEREBY PROVIDING A MEANS FOR REGULATING THE FLOW OF AIR WHILE ABSORBING SOUND. 